1. Field of the Invention
The present invention relates generally to catheters having a bipolar electrode tip for transmitting electrical signals to and from a particular internal region of an animal's body and more specifically to catheters having a plug portion for connection to an electronics unit, an electrode portion for electrically contacting a portion of the animal's body, and a lead portion extending between the plug portion and the electrode portion, the lead portion including a pair of spiral conductors disposed in a bilumen tube, and the electrode portion including an anode ring and a cathode tip spaced from the anode ring, the cathode tip being electrically connected to one of the lead portion conductors and the anode ring being connected to the other of the lead portion conductors.
2. Background of the Prior Art
Transmission of electrical signals to and from various internal regions of an animal's body is an essential aspect of many modern diagnostic and corrective medical procedures and techniques. For example, the use of an artificial pacemaker in treating heart block, which is a failure of the body to provide the necessary electrical stimulus to maintain the steady rhythmic beating of the heart, includes transmitting electrical signals between a battery-powered electronic unit and the surface of the heart. In accordance with modern systems, the electronic unit senses an interruption in the heartbeat rhythm and, in response, transmits an electrical signal to the heart to stimulate the heart to its proper rhythm.
In the prior art, such procedures have been implemented using a system including an electronic unit and a catheter. The electronic unit generally has included an electronic circuit for sensing the existence or non-existence of body-produced electrical stimuli and/or for providing artificial electrical signal stimuli; a battery for powering the electronic circuit; and connector jacks for connecting the electronic circuit to the catheter. Examplary electronic units are described in U.S. Pat. No. 3,857,398, issued to Rubin on Dec. 31, 1974, and U.S. Pat. No. 3,857,399, issued to Zacouto on Dec. 31, 1974.
Catheters of the prior art have included five principal parts: a plug portion for cooperating with the jacks of the electronic unit; two conductors for conducting the electrical signals to and/or from the region of the body to be stimulated or at which naturally produced stimuli are to be sensed; an electrode portion for electrically contacting the region of the body to be sensed and/or stimulated; and an insulation tube connecting the plug and electrode portions and through which the conductors extend.
According to the prior art configuration to which the present invention is most closely related, the plug portion includes a Y-shaped casing made of silicone rubber. Single passages extend through each of the arms of the casing and into the base of the casing. The passages extend parallel to one another through the base of the casing. The plug portion of such a configuration further includes hollow elongate pins extending parallel to one another from the tips of the arms of the casing, the chamber of each pin communicating with the passage through the art from which the pin extends. The pins are of a configuration that will mate with the jacks of the electronic unit.
The conductors of such a prior art configuration are spiralwound wires of highly flexible metal, the winding of the wires being such that adjacent windings are in full contact with one another when at rest and such that a passage extends through the windings. One end of each conductor extends through one of the passages of the plug portion and is electrically connected to the pin of the plug portion communicating with that passage.
The insulation tube of such a configuration includes a bilumen tube of circular cross section. One end of the bilumen tube abuts the tip of the base of the casing of the plug portion such that the passages of the base communicate with the passages of the bilumen tube. The conductors, therefore, extend directly into and through the passage of the bilumen tube.
The electrode portion of such a prior art configuration is shown in FIG. 2 of the drawings. As shown therein, electrode portion 11 includes metallic annular anode ring 13 spaced a distance X from the end of insulation tube 15 opposite the plug portion and having an outer diameter substantially equal to that of tube 15. Conductors 17, 19 extend from the end of tube 15 into ring 13, conductor 17 terminating within ring 13 and conductor 19 passing through the entirety of ring 13 and a distance Y beyond ring 13. Electrode portion 11 further includes resistance weld points 21, 23 electrically connecting and physically securing conductor extension 17 to the inner surface of anode ring 13; cylindrical slug 25 disposed in the passageway of conductor extension 17 for facilitating welding of extension 17 to ring 13; unilumen tube 27 made of silicone rubber abutting tube 15 and through which conductor 19 extends whereby conductor 19 is electrically insulated from extension 17 and ring 13; cathode tip 29 having socket stem 30 and blind socket passage 31 within which extreme end 33 of conductor 19 is secured, unilumen tube 27 being expanded about the outer periphery of stem 30; and silicone rubber potted regions 37, 39. Thus, electrode portion 11 has bipolar spaced electrodes, anode ring 13 being the proximal (nearest the electronic unit) electrode and tip 29 being the distal electrode.
Potted region 37 has major portion 41 extending between ring 13 and tube 15 and filling in the spaces between conductor 17 and unilumen tube 27 and between the ends of unilumen tube 27 and tube 15. Portion 41 has a generally cylindrical outside surface having a diameter slightly greater than that of tube 15. Another portion of potted region 37 extends into ring 13. A third portion 43 of potted region 37 extends over the outside of tube 15 and terminates at feather edge 45.
Potted region 39 surrounds the portion of unilumen tube 27 extending between ring 13 and cathode tip 29 as well as socket step 30 of tip 29. Potted region 39 is vulcanized to ring 13 with a portion of potted region 39 extending into ring 13. The outer surface of potted region 39 adjacent ring 13 is contiguous with the outer surface of ring 13 whereby unilumen tube 27 is asymetrically disposed in potted region 39 adjacent ring 13. The position of tube 27 in potted region 39 is such that tube 27 is coaxial with the outer surface of potted region 39 adjacent tip 29. Thus, the axes of potted region 39 and unilumen tube 27 do not assume the same direction between ring 13 and tip 29.
One or more of the above-described catheter features are disclosed in the following U.S. Patents:
______________________________________ U.S. Pat. No. Issued Inventor ______________________________________ 3,974,834 August 17, 1976 Kane 4,046,151 September 6, 1977 Rose 3,769,984 November 6, 1973 Muench 3,348,548 October 24, 1967 Chardack 4,057,067 November 8, 1977 Lajos 4,010,755 March 8, 1977 Preston 3,853,398 December 31, 1974 Rubin 3,788,329 January 29, 1974 Friedman ______________________________________
All of the above-listed patents show bipolar or dual electrodes for the electrode portion. Chardack, Lajos and Friedman show the use of spiral conductors to give flexibility to the catheter. Muench, Chardack, Preston and Rubin show one conductor passing through a ring shaped electrode and connecting to a tip electrode spaced apart from the ring, and the other conductor terminating at and connecting to the internal surface of the ring electrode. Chardack shows slugs inserted in the ends of the spiral conductors where they are attached to the ring and tip electrodes.
Some variations from the above-described prior art configuration but pertinent to the invention are shown in the above-listed patents. Thus, Muench shows the use of stranded conductors that are attached to the electrode by crimping. Chardack shows the bilumen insulation tube extending into the anode ring. One lumen of the bilumen tube is cut off and the conductor extending through that portion is attached to the internal surface of the ring. The other lumen extends through the ring and to the tip electrode. Silicone rubber is molded about a portion of the tip electrode, about the lumen portion extending to the tip electrode, and within the anode ring such that a portion of the rubber overlaps the bilumen tube within the ring.
Kane, Rose, Chardack and Friedman show Y-shaped plug portions.
Kane and Rose show a bilumen tube with spiral conductors, one conductor extending into the terminating at the anode ring, and the other conductor extending through the ring and terminating in a tip electrode spaced from the anode ring. The latter conductor is potted in silicone rubber.
Various alternative forms of catheters are shown in the following U.S. Patents:
______________________________________ U.S. Pat. No. Issued Inventor ______________________________________ 3,596,662 August 3, 1971 Bolduc 3,844,292 October 29, 1974 Bolduc 3,875,947 April 8, 1975 Jula 3,888,260 June 10, 1975 Fischell 4,010,758 March 8, 1977 Rochland 4,033,355 July 5, 1977 Amundson ______________________________________
Bolduc '662 is of interest showing molding equipment. Bolduc '292 shows an electrode with a spear point such as that shown in FIG. 2.
A problem encountered in the use of catheters of the abovedescribed prior art configuration is a tendency of various connections in the electrode portion and the junction of the insulation tube and electrode portion including metal-to-metal connections, rubber-to-rubber connections and metal-to-rubber connections, to fail. Failure occurs in the light of constant movement of the body, including involuntary movement of internal organs, that causes shear and stres forces to be applied to the electrode portion and the junction of the electrode portion and insulation tube. Such failures often result in body fluid leakage all the way to one or both of the conductors causing an undesirable change in system sensitivity. Furthermore, a short circuit may be caused between the conductors or the connection of a conductor to its corresponding electrode may be opened.
Another problem persisting in the prior art catheters of the type described has been a tendency of the tube extending between the ring electrode and the tip electrode to twist whereby proper insertion of the electrode portion is sometimes hampered.